CANBERRA Airport has revealed designs for a new high-speed rail terminal linking to a Sydney train line no one has promised to build.

In a bid to pressure the government to accept the national capital as the second Sydney airport site, Canberra Airport managing director Stephen Byron committed to building the $140 million terminal within two years if the multi-billion dollar train line to Sydney was given approval.

The plan to link Sydney with a one-hour, 300km train trip to an upgraded Canberra Airport has been championed by Premier Barry O'Farrell but has been derided by senior Liberals and the federal government for being too far away.

Transport Minister Anthony Albanese labelled the new designs "premature'', saying he had already ruled out a second airport so far away from Sydney and that studies into an eastern seaboard high-speed rail network were not yet finalised.

"It's a bit premature to talk about building a terminal when there's no track or train,'' he said. "I have consistently said Sydney's second airport will not be in Canberra.''

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